Chemical industry - Unit 6 Flashcards
What is meant by dynamic equilibirum?
1 - Rate of forward reaction equals rate of reverse reaction in a closed system
What do you talk about when asked ‘Comment on the choice of conditions’ (2)
1 - Yeild
2 - Rate
What is the effect of a catalyst on equillibrium?
1 - No effect on equillibirum
2 - Increases rate of forward and reverse reaction equally by providing alternative reaction pathway with a lower Ea
What is NH4+?
The ammonium ion
What is the name of N2O?
dinitrogen oxide
What is the apperance of NO, NO2, N2O?
NO = colourless gas, turns to brown NO2 in air
NO2 = brown gas
N2O = colourless gas
How is NO formed? (3)
1 - Combustion in engines
2 - Thunderstorms
3 - In soil by denitrofying bacteria
How is NO2 formed?
from oxidation of NO in atmosphere
How is N2O formed?
In soil by denitrfying bacteria
What is the reactivity of N2O, NO, NO2 (2)
NO + NO2 = most reactive as radicals
N2O = less reactive as not a radical
What is the test for a nitrate (V) ion and equation? (4)
1 - Add Davardas alloy - Al (reducing agent)
2 - Add NaOH
3 - Add sample to a test tube + heat
4 - NH3 gas turns damp red litmus paper blue
What is the test for ammonium ions? (3)
1 - Add NaOh to sample
2 - Add to test tube + heat
3 - NH3 gas will turn damp red litmus paper blue
How do you make sulfuric acid? (4)
1 - Extraction of sulfur
2 - Conversion of sulfur to sulfur dioxide
3 - Conversion of sulfur dioxide to sulfur trioxide
4 - Conversion of sulfur trioxide to sulfuric oxide
What is rate of a reaction?
How quickly reactants are converted into products
What are the experimental methods that can be used to measure the rate of reaction? (5)
1 - Volume gas produced - gas syringe
2 - Mass lost (gas lost)
3 - pH changes - pH probe
4 - Coloured product made or reactant used - colormetry
5 - Titration - taking samples at a known time - quenching samples (stop/slow down reaction) - titrate samples
What are the issues with measuring the mass lost of a gas?
The mass of the gas could be so little that the mass scale would not detect a loss in mass
How can you quench a smaple? (2)
1 - If acid you could add a base to neutralise reaction
2 - Sit on a bed of ice
What is the equations and catalyst for production of sulfuric acid? (3)
1 - S + O2 –> SO2
2 - SO2 + 1/2 O2 <—-> SO3 (contact process)
V2O5 (catalyst)
3 - SO3 + 1/2 O2 –> SO4
What are the possible units for rate? (3)
1 - moldm-3s-1
2 - cm3s-1
3 - gs-1
What is the use of rate equations?
Allow estimates to be made about the impact of a factor on the rate of a reaction without having to carry out experiments
What does the gradient of a graph give you?
The rate
Explain the rates on graph? (2)
1 - Steep gradient gives fast rate - conc. reactnat high
2 - Shallow gradient gives slow rate - conc. reactant falls
How can you find initial rate?
Draw a tangent to the curve at t=0
What does straight line graph mean?
rate directly proptional to conc. reactant
What is k (lower case) ?
rate constant
What does k vary with?
temp
Why could the units of k be the same for two different reactions?
Because the overall order if the two reactions is the same
What is the unit of k when overall order of a reaction is 2nd order?
dm3mol-1s-1
What is the unit of k when overall order of a reaction is 0 order?
moldm-3s-1
What is the unit of k when overall order of a reaction is 1st order?
s-1
What does it mean if a reaction is 1st order?
Doubling the conc. doubles the rate
What does it mean if a reaction is 2nd order?
doubling the conc., quadruples the rate
What does it mean if a reaction is 3rd order?
conc. has no effect on rate
What is the most important factors for determining rate? (3)
1 - Most important - Ea
2 - Then temp
3 - Then conc.
What is the Arrhenius used for?
To calulate the impact of changing:
1) Ea (by a catalyst)
2) Temp
on rate of reaction
What happens to the rate of reaction with a 100c temp rise?
rate roughly doubled, (kx2)
Describe effect of 100c temp rise on rate of reaction? (2)
1 - Number of collisions with energy =Ea or >Ea almost doubles
2 - So rate roughly doubles
Describe the effect of decreasing the Ea on rate? (2)
1 - significantly increases the no of collisions with energy =Ea or >Ea
2 - Therefore increases rate
How do you find the order of reaction WRT a certain reactant? (3)
1 - Draw a tangent at the origin of diff graphs + find graident to find initial rate values
2 - Plot initial rate against conc.
3 - Graphs shape will determine order
What can the average rate of reaction be proportional to?
1/time
What is T?
Temp
What is t?
time
How can half lives be used to detrmine order of reaction? (2)
1 - If half lives are constant then reaction 1st order
2 - 0 + 2nd order don’t have constant half lives
What is the half-life?
The time taken for the conc. of a substance to half
What is the rate-determining step?
The slowest step in the reaction mechanism
How can the rate-equation be used to find info about the rds? (3)
1 - Sustances not in the rate equation are not in the rds, they are in a faster step
2 - Susbatances in rate equation are in rds
3 - Order of reaction WRT each substance will tell you realtive no. moles/molecules of the substance involved in the rds
Why are some steps in a mechanims slower than others? (3)
1 - Step has a higher Ea
2 - Only, small no. reactants have >/= energy to overcome Ea each second + turn into products
3 - rate reaction slow
Where can the rds occur in a multi-step mechanism?
rds can come at any point
In a multi-step reaction, what will be the rds?
The step with the highest Ea
How does the energy of intermediates + reactnts+ products of the same reaction compare?
Intermediates have higher energy than products + reactants
What is a raw material, examples?
Something that is unprocessed
1 - Air
2 - Crude oil
3 - Natural gas
What are feedstocks, example?
processed raw material
1 - Ethene
What is a co-product?
Useful product of a reaction
What is a by-product? (2)
1 - Not useful products made by secondary reactions
2 - Must be disposed of
How can thermal energy be conserved?
Using heat exchangers
What is a hazard?
The potential that a hazadrous substance has to cause harm
What is a risk?
The liklihood the hazardous substance will cause harm under the conditions of its use
What is the risk of flammable gases and control methods? (2)
1 - Explosions, fires
2 - Store in flameproof cyclinders
What is the risk of acidic gases and control methods? (2)
1 - Burns
2 - Regular checking of plant for leaks
What is the controls methods for toxic emmissions? (2)
1 - Monitor level of emmissions
2 - Evacuation procedures practiced
How doe you turn NH3 into NH4+?
Add acid
If something is 0 order does it go in the rate equation?
No
What is the order of a substance if it is in a fast step?
0 order
What is the order of a substance if it is in a slow step?
2nd or 1st
If a reaction is endothermic and you increase the temp, what will happen to the yeild?
1 - Endothermic reaction dcreases temp
2 - Therefore, higher temp favours endothermic reaction
3 - Therefore yeild increases
If a reaction is exothermic and you increase the temp, what will happen to the yeild?
1 - exothermic increase temp
2 - Therefore exothermic reaction not favoured
3 - Yield decreases
